A supply of well-characterized nonhuman primates (NHP) is essential for use in biomedical research as models of human diseases including AIDS. In particular, animals free of specific viral agents known to cause disease in humans as well as those known to confound research studies are critical to achieving research goals. The Tulane National Primate Research Center (TNPRC) has one of the largest rhesus monkey breeding colonies in the US. This resource has provided animals for NIH funded AIDS research projects for several decades. This resource is essential to the success of many NIH-funded investigators throughout the US. Several years ago the TNPRC established the goal of converting its rhesus monkey breeding colony completely to specific pathogen free (SPF) status. A major step toward accomplishing that goal was the award of this U24 grant in 2002. This application requests funds for continued support the TNPRC AIDS SPF rhesus monkey breeding colony. During the current funding period the colony has become self-sustaining consisting of 1172 animals at the time of writing. The entire TNPRC AIDS SPF colony supported by U24 and U42 grants is the largest in the NCRR/OAR funded program, comprising 37% of the total animals reflected in the current program census. The TNPRC U24 supported SPF colony is also notable because a portion of the population is negative for up to five additional agents (total of nine) important as opportunistic agents in AIDS (SPF9/expanded SPF). Funding from the U24 over the next grant period will be used specifically to support per diem, testing to monitor viral status, individual ad population genetics, and MHC characterization. Program income and other sources of funds will be used to fund clinical pathology laboratory charges, pathology support, clinical care of ill animals, renovation of breeding facilities, parasitology diagnostics, security, genome banking and genome sequencing.